Application Webhooks Post not working - giving error for base URL

I am using Application Webhook API to create a webhook for application. After I followed the following documentation, I am getting error for base_url attribute.

Documentation I followed -

I tried different URLs but getting same error everytime. Here are few URLs
“base_url”: “”,
“base_url”: “”,

Error response -
“field”: “base_url”,
“name”: “ApplicationWebhookValidationError”,
“reason”: “value must be absolute”

Can someone help with this issue?